Systems, materials, and methods for recovering material from bedrock using supercritical argon compositions

Claim of Priority

This application is a U.S. national stage filing under 35 U.S.C. §371 of International Application No. PCT/US2011/050236filed Sep. 1, 2011entitled “Systems, Materials, and Methods for Recovering Material from Bedrock Using Supercritical Argon Compositions,” the disclosure of which is incorporated by reference in its entirety.

Hydraulic fracturing (also termed “fracking”) is a method of removing material from strata or zones within bedrock using a pressurized material pumped into a bore well drilled into the bedrock. The pressurized material (also termed “fracking material” or “fracking mixture”) diffuses into small openings or fissures within bedrock zones and expands them into larger fracture structures. These larger fractures allow the underground material to be withdrawn from the bedrock more readily than if the original fissures were not enlarged. The material recovered from the underground source is then pumped into facilities where the fracking mixture can be readily separated from the material recovered from the bedrock.

Fracking methods have been used extensively in the recovery of petroleum related materials such as natural gas and oil from oil shale. Another application for this technique may be found in the recovery of water from water-bearing zones or strata within bedrock. The use of hydraulic fracturing for water recovery may prove beneficial, especially in regions lacking readily accessible surface or near-surface water, and where deeper aquifers may be found.

Unlike petroleum materials obtained in this manner, water extracted by means of fracking must be potable for human, animal, and agricultural use. Therefore, a fracking mixture used to recover water must have a minimal effect on water potability.

In an embodiment, a material for hydraulic fracturing includes a supercritical fluid comprising at least about 95% argon and at least one proppant. Additional embodiments of the hydraulic fracturing material may include at least a portion of argon-37 ( 37 Ar), a gas, a gel, and/or a foaming agent.

In an embodiment, a system for extracting material from bedrock includes a source of a supercritical fluid comprising at least about 95% argon, a source of at least one proppant, a mixing device configured to mix the supercritical fluid and the proppant into a fracking mixture, a bore well into the bedrock, a pump configured to pump the fracking mixture into the bore well, and a recovery unit configured to recover the material from the bedrock.

In an embodiment, a method for extracting material from bedrock comprises providing a source of a supercritical fluid comprising at least about 95% argon, providing a source of at least one proppant, mixing the supercritical fluid and the proppant to provide a fracking mixture, pumping the fracking mixture into a bore well, and recovering the material from the bedrock.

In another embodiment, a method for recovering water from bedrock comprises providing a bore well extending from a land surface to, into or through at least one zone of bedrock containing water, providing a source of a supercritical fluid comprising at least about 95% argon, providing a source of at least one proppant, mixing the supercritical fluid and the proppant to provide a fracking mixture, pumping the fracking mixture into the bore well, allowing the fracking mixture to develop a number of fracture structures within the bedrock, and recovering water from the bore well.

In another embodiment, a structure for recovering water from bedrock comprises a bore well extending from a land surface to, into or through at least one zone of bedrock containing water, and a fracking mixture disposed within the bore well, the fracking mixture comprising, a supercritical fluid comprising at least 95% argon, and at least one proppant.

FIG. 1 illustrates a section of bedrock comprising multiple zones or strata in accordance with the present disclosure.

FIG. 2 a illustrates a water-bearing zone of bedrock comprising multiple fissures in the zone prior to hydraulic fracturing in accordance with the present disclosure.

FIG. 2 b illustrates a water-bearing zone of bedrock after hydraulic fracturing in which the fissures have been expanded into fracture structures in accordance with the present disclosure.

FIG. 2 c illustrates an expanded view of a fracture structure including proppant particles in accordance with the present disclosure.

FIG. 3 a illustrates one embodiment of a system for recovering material from a zone in bedrock in accordance with the present disclosure.

FIG. 3 b illustrates another embodiment of a system for recovering material from a zone in bedrock in accordance with the present disclosure.

FIG. 4 illustrates various embodiments regarding the placement of bore wells into bedrock zones or strata in accordance with the present disclosure.

FIG. 5 illustrates various embodiments regarding the use of seals within bore wells in accordance with the present disclosure.

Hydraulic fracturing (“fracking”) methods are most commonly associated with recovery of petroleum related materials from deep bedrock structures. The fracking material used in the process may be a complex mixture incorporating a base fluid, proppants, gels, and breakers, among other additives. In some petroleum-related fracking procedures, fracking material components have included diesel fuel, isopropanol, hydrochloric acid, and other components with potentially hazardous properties. Such fracking materials, if not completely removed during a recovery operation, may pose an environmental hazard if they leach into local groundwater. The hazardous properties of such fracking materials is even more important if subsurface water is being recovered, since it may not be possible to remove all the fracking material from the water. It is therefore desirous to develop a fracking material that may pose a minimal hazard both to the environment and to potential consumers of water recovered by this method. The present disclosure is directed to the use of supercritical argon as the basis for the fracking material. Argon is an inert gas, and has no specifically identified toxicity to animals or plants. Argon in the supercritical state may be used as a low viscosity carrying fluid for proppants to assist in fracturing fissures in subsurface aquifers, thereby allowing improved recovery of water or other materials from bedrock.

FIGS. 1 and 2 a illustrate bedrock compositions in which hydraulic fracturing can provide an effective way to extract material from bedrock. In FIG. 1 , a cross-section of bedrock ( 100 ) is displayed illustrating multiple overlaying zones or strata. Some of the zones may not contain material that may be extractable using the fracking process ( 120 a - d ). A surface layer ( 120 a ), for example may comprise silt, gravel, or pebbled clay. Deeper layers may include dolomite, shale, and siltstone ( 120 b, c, d ). Other zones may contain extractable material such as water. In one embodiment, water may be trapped in deep aquifers comprising sandstone ( 140 a , 140 b ). While bedrock strata or zones may overlay each other completely, as illustrated with zone ( 120 a ) completely overlaying zone ( 120 b ), zones may interdigitate or intrude into one another. As illustrated, a water-bearing zone ( 140 a ) may intrude into a non-water-bearing zone ( 120 d ). In addition, multiple water-bearing zones may overlay each other, separated by a non-water-bearing zone as illustrated by zone ( 140 a ) overlaying zone ( 140 b ) separated by a third zone ( 120 d ). Although water may be one material available for extraction by hydraulic fracturing, it is understood that other materials of interest may include precious metals, natural gas, or other non-aqueous materials.

FIG. 2 a illustrates an expanded view of one section of a water-bearing zone ( 200 ). In particular, the bedrock in this zone comprises fissures or narrow cracks ( 210 ) in which the material of interest, such as water, may collect. These fissures may be too narrow to permit water or other material to be easily extracted through a surface-drilled bore well. The fissures, however, may be enlarged using a fracking material or fracking mixture. A fracking material introduced under pressure through a bore well may widen or enlarge the fissures into wider fracture structures. FIG. 2 b illustrates these enlarged fracture structures ( 220 a ) caused by the fracking mixture. If the fracking mixture solely comprises a liquid, gas, or other material readily removed from the bedrock, the fracture structures can collapse, thereby preventing continued extraction of the material of interest. Frequently, the fracking mixture also comprises some material (a proppant) that is left within the fracture structures to keep the fracture structures open. FIG. 2 c , an expanded view of FIG. 2 b , illustrates the effect of such proppants on the fracture structures. The proppant particles ( 230 a - c ) remain within the fracture structure ( 220 b ), keeping the fracture structure open.

A material for hydraulic fracturing (or a fracking material or fracking mixture) can comprise a variety of materials and components. In one embodiment, the fracking material comprises a supercritical fluid comprising at least 95% argon, in addition to at least one proppant material. A supercritical fluid is a material that shares properties of both liquids and gases, and is effective for penetrating narrow fissures within bedrock. A supercritical fluid is characterized by a critical temperature and critical pressure, which are the minimal temperature and pressure at which the supercritical fluid can be maintained. For argon, the critical temperature is about −122 degrees C., and the pressure is about 50 atmospheres (5,066 KPa). An embodiment of the hydraulic fracturing material comprises a supercritical fluid comprising at least 95% argon maintained at a temperature above about −122 degrees Celsius, a pressure above about 50 atmospheres (5,066 KPa), and at least one proppant. Another embodiment of the hydraulic fracturing material comprises at least 95% argon maintained at a temperature between about −122 degrees Celsius and about 175 degrees Celsius, at a pressure above about 50 atmospheres (5,066 KPa), and at least one proppant. In another embodiment, some portion of the argon may comprise argon-37. Argon-37 may be monitored to determine if any residual fracking material diffuses from its introduction site to other areas in the environment.

In some embodiments, the proppant comprises, as non-limiting examples, sand grains, resin-coated sand, glass, high-strength bauxite ceramic material, and/or high strength non-bauxite ceramic material. In some embodiments, the proppant comprises, as non-limiting examples, a plastic, such as Bakelite, melamine, phenols, phenolics, epoxy, styrenics, acrylics, vinyls, phenol-formaldehyde, tetrafluroethylene, urea-formaldehyde, novolac, polycarbonate, lexan, benzoxazine, polyesters, polyamides, nylon, polyetherimide, polybenzimidazole, polyamide-imide, polyvinyl chloride, benzoguanamine, urea, and/or glycoluril.

In some further embodiments, the proppant may have, as non-limiting examples, a spherical, ellipsoidal, rectangular, polygonal, jagged, or uneven shape. In some embodiments, the proppant has a size of about 30 nm to about 3 mm. In some further embodiments, the supercritical argon is maintained at a pressure—greater than about 50 atmospheres (5,066 KPa)—and at a temperature—greater than about −122 degrees Celsius and below about 175 degrees Celsius—so that the density of the supercritical argon has approximately the same density of the proppant mixed with it.

In another embodiment, the fracking material may further comprise a gas characterized as being environmentally benign and non-toxic. Non-limiting examples of such a gas include noble gases (krypton or xenon), carbon dioxide, nitrogen, and water vapor.

In another embodiment, the fracking material may also include a gel. Such a gel may include, as non-limiting examples, an inorganic gel, a wax, and/or an oligomer. The gel may comprise a linear polymer, non-limiting examples being a functional polyethylene, polypropylene, polyolefin, polyethylene oxide, polypropylene oxide, copolymers of polyethylene oxide and polypropylene oxide, vinyl ether, polyesters, polyamides, polycarbonate, acrylics, styrenics, vinyl ketones, protein, amino acids, collagen, pectin, gelatin, agarose, amylose, poly lactic acid, and/or poly galactic acid. In an alternative embodiment, the gel may comprise a branched or cross-linked polymer, with non-limiting examples being polyurethane, polyurea with a carboxylate functionality, cellulostics, branched or cross-linked acrylics, low molecular weight epoxy resins, branched or cross-linked polyesters, branched or cross-linked polyamides, branched or cross-linked polycarbonate, branched or cross-linked vinyl ketones, fluorinated resins, branched or cross-linked protein, branched or cross-linked amino acids, branched or cross-linked collagen, branched or cross-linked pectin, branched or cross-linked gelatin, branched or cross-linked agarose, and/or branched or cross-linked. amylose. The amount of gel included in the hydraulic fracturing material may be selected to impart a desired viscosity to the fracking material.

In yet another embodiment, the fracking material may also include a foaming agent. A foaming agent may be included in the fracking material to reduce the amount of supercritical fluid in the fracking mixture. Non-limiting examples of such foaming agents include ceramic hollow microspheres, and/or plastic hollow microspheres. Other foaming agents may include non-toxic surfactants such as cocamide MEA, cocamidopropyl betaine, coceth-4, coceth-7, and coconut alcohol ethoxylate. Additionally, the supercritical argon may be maintained at a pressure and temperature so that the density of the supercritical argon is approximately the same as the density of the foaming agent.

The various embodiments of a fracking mixture as disclosed above may be incorporated into a system for extracting material from bedrock. While the material to be extracted may be water or comprise water, it is understood that the material may comprise other non-aqueous materials, non-limiting examples being precious metals and natural gas.

One embodiment of such a fracking system ( 300 ) is illustrated in FIG. 3 a . The fracking system includes a source of argon ( 310 a ), a source of at least one proppant ( 315 a ), and a mixing device ( 320 a ) to mix the argon and proppant together to provide a fracking mixture. As disclosed above, the fracking mixture may comprise other components in addition to the argon ( 310 a ) and proppant ( 315 a ). While not explicitly illustrated in FIG. 3 a , it is understood that mixing device ( 320 a ) can also be configured to mix other components into the fracking mixture including at least one gas, at least one gel, and/or at least one foaming agent. Such additional components may be supplied to the mixing device from sources specific to those components.

The fracking mixture may then be pumped into a bore well ( 330 a ) cut into the bedrock (not shown) through a pump ( 325 a ). The pump ( 325 a ) may be used to recover the material from the bore well ( 330 a ). The recovered material may then be placed in a recovery unit ( 340 a ) which allows the separation of the water ( 350 a ) from any residual components of the fracking mixture, or other material leached from the bedrock. The pump ( 325 a ) may comprise any suitable pump for the application including, as one non-limiting example, a bilge pump. In addition, the pump ( 325 a ) may attain a suitable pump rate and pressure for the application including, as non-limiting examples, a pump rate up to about 100 barrels per second (15.9 cubic meters per second) and a pumping pressure up to about 15,000 psi (103,421 KPa). While a single pump ( 325 a ) is illustrated in the figure, it is understood that additional pumps may be included. Such additional pumps may pump other materials into the bore well ( 330 a ) or else pump the water and residual fracking material from the well.

An alternative embodiment of a fracking system is illustrated in FIG. 3 b . In this embodiment, the argon from its source ( 310 b ) is mixed in a mixing device ( 320 b ) with at least one proppant, obtained from its source ( 315 b ). The material produced by this first mixing device may then be further mixed with another component, such as a gas obtained from a gas source ( 355 ) in a separate mixing device ( 360 ). While not explicitly illustrated in FIG. 3 b , it is understood that other components may be mixed into the fracking mixture through the operation of additional mixing devices. In addition, it is understood that there is no specific order of mixing such components. Such components may include at least one gel and/or at least one foaming agent. These components may be provided to the separate mixing devices from sources specific to them.

The fracking mixture may be introduced into a bore well ( 330 b ) through a pump ( 325 b ). The material recovered from the bore well may then be provided to a recovery unit ( 340 b ) in which the material, such as water ( 350 b ), is separated from any residual fracking mixture or other material leached from the bedrock. As described previously, multiple pumps may be used to introduce material into, or extra material from, the bore well ( 330 b ).

The fracking system disclosed above, and the fracking mixture also previously disclosed, may be used for extracting material from bedrock. While the material extracted from the bedrock may be water or comprise water, it is understood that the material can comprise non-aqueous materials, non-limiting examples being precious metals or natural gas. In one embodiment, a method for extracting material from bedrock comprises providing a source of a supercritical fluid comprising at least about 95% argon, providing a source of at least one proppant, mixing the supercritical fluid and the proppant to provide a fracking mixture, pumping the fracking mixture into a bore well, and recovering the material from the bedrock.

As previously disclosed, the fracking material may further comprise at least one gas, at least one gel, and/or at least one foaming agent. Alternative embodiments of the method may further include providing any one or more of these materials and mixing them into the fracking material. It is understood that mixing any of these additional materials may be accomplished by a single mixing device or multiple mixing devices. In addition, the order of mixing the components need not be specifically fixed. In an alternative embodiment, the argon comprises at least a portion of argon-37, and the method further includes tracing the argon-37 within the bedrock. As examples, tracing the argon-37 may be accomplished through sampling aquifer water through drilling into bedrock, or monitoring water seepage from springs. In another embodiment, the amount of gel included in the fracking mixture may be selected to impart a selected viscosity to the fracking mixture. In another embodiment, the temperature and pressure of the fracking mixture may be chosen so that the supercritical argon has a density about the same as the proppant. In yet another embodiment, the temperature and pressure of the fracking mixture may be chosen so that the supercritical argon has a density about the same as the foaming agent.

In another embodiment, the pumping step includes pumping the fracking mixture into the bore well at a pressure up to about 15,000 psi (103,421 KPa) and at a rate up to about 100 barrels per second (15.9 cubic meters per second).

The fracking system disclosed above, and the fracking mixture also previously disclosed, may be used for extracting water from bedrock. In one embodiment, a method for extracting water from bedrock comprises providing a bore well extending from a land surface to, into, or through at least one zone of bedrock bearing water, providing a source of a supercritical fluid comprising at least about 95% argon, providing a source of at least one proppant, mixing the supercritical fluid and the proppant to provide a fracking mixture, pumping the fracking mixture into the bore well, allowing the fracking mixture to develop a plurality of fracture structures within the bedrock, and recovering water from the bore well.

As previously illustrated, in FIG. 1 , bedrock may comprise multiple water-bearing zones that may overlay each other, either directly or with a non-water-bearing zone between them. FIG. 4 illustrates how the bore well may be disposed with respect to these different geological layers. Non-water-bearing zones or strata ( 420 a - d ) may comprise, in non-limiting examples, loose gravel, dolomite or shale. Water-bearing zones ( 440 a, b ) may intrude into these strata and may overlay each other directly, or be separated by non water bearing zones ( 420 d ). A bore well may be drilled into the bedrock to various depths to retrieve water from one or multiple water-bearing zones. Thus, bore well ( 430 a ) exemplifies a bore well drilled just to the top of water-bearing zone ( 440 a ). The bore well may also be bored into the water-bearing zone ( 430 b ). Alternatively, the bore well ( 430 c ) may be bored through one water-bearing zone ( 440 a ) and into a second, underlying water-bearing zone ( 440 b ). As illustrated in FIGS. 2 a and 2 b , the original fissures in the water bearing zone ( 210 ) may be induced to expand into fracture structures ( 220 a, b ) under the pressure exerted by the fracking mixture.

As previously disclosed, the fracking mixture may further comprise other components including at least one gas, at least one gel, and/or at lest one foaming agent. Alternative embodiments of the method may further include providing any one or more of these materials and mixing them into the fracking material. It is understood that mixing any of these additional materials may be accomplished by a single mixing device or multiple mixing devices. In addition, the order of mixing the components need not be specifically fixed. In another embodiment, the argon in the fracking mixture may comprise at least a portion of argon-37, which may be traced within the bedrock using techniques previously disclosed. In another embodiment, the amount of gel included in the fracking mixture may be selected to impart a selected viscosity to the fracking mixture. In another embodiment, the temperature and pressure of the fracking mixture pumped into the bore well may be chosen so that the supercritical argon has a density about the same as the proppant. In yet another embodiment, the temperature and pressure of the fracking mixture pumped into the bore well may be chosen so that the supercritical argon has a density about the same as the foaming agent.

In another embodiment, the pumping step includes pumping the fracking mixture into the bore well at a pressure up to about 15,000 psi (103,421 KPa) and at a rate up to about 100 barrels per second (15.9 cubic meters per second).

In a further embodiment, at least one seal is disposed into the bore well, as illustrated in FIG. 5 . Non-limiting examples of such seals include mechanical packer seals and inflatable packer seals. The section of bedrock illustrated in FIG. 5 may include multiple strata or zones that do not contain water ( 520 a - e ) as well as zones containing water ( 540 a, b ). In some embodiments, it may be desirous to employ the fracking method on one water-bearing zone at a time. Thus, bore well ( 530 a ) illustrates the use of a seal ( 580 a ) inserted and activated at a depth to isolate one water-bearing zone ( 540 a ) while a second water-bearing zone ( 540 b ) is subjected to the fracking method. In one embodiment, the water from an underlying zone ( 540 b ) may then be retrieved in isolation from the overlaying zone ( 540 a ). In another embodiment ( 530 b ), the seal may be deactivated and moved from its first depth position ( 580 b ) and repositioned and reactivated at a second depth ( 580 c ). This may permit the fracking mixture to enter the overlying zone ( 540 a ) and isolate the underlying zone ( 540 b ). Multiple seals may also be used within the same bore well ( 530 c ). In this embodiment, it may be desirous to isolate an underlying water-bearing zone ( 540 b ) from an overlying water-bearing zone ( 540 a ), as well as prevent contaminants, such as hydrocarbons or salt-water, from entering the water from another zone ( 520 e ).

The fracking mixture previously disclosed, may be incorporated into a structure for recovering water from bedrock, the structure comprising a bore well extending from a land surface to, into, or through at least one zone of bedrock containing water, and a fracking mixture disposed within the bore well, the fracking mixture comprising, a supercritical fluid comprising at least 95% argon, and at least one proppant.

As previously disclosed, the fracking mixture may further comprise other components including at least one gas, at least one gel, and/or at lest one foaming agent. In another embodiment, the argon in the fracking mixture may comprise at least a portion of argon-37. In still another embodiment, the amount of gel included in the fracking mixture may be selected to impart a selected viscosity to the fracking mixture. In another embodiment, the temperature and pressure of the fracking mixture pumped into the bore well may be chosen so that the supercritical argon has a density about the same as the proppant. In yet another embodiment, the temperature and pressure of the fracking mixture pumped into the bore well may be chosen so that the supercritical argon has a density about the same as the foaming agent.

In order to illustrate the various features disclosed above, the following non-limiting examples are provided.